Amzel L M, Poljak R J, Saul F, Varga J M, Richards F F
Proc Natl Acad Sci U S A. 1974 Apr;71(4):1427-30. doi: 10.1073/pnas.71.4.1427.
IgG New binds ligands such as orceine, menadione, and uridine with a low affinity (K(0) about 1 x 10(3) liter/mol) and a gamma-hydroxy derivative of vitamin K(1) with a higher affinity (K(0) = 1.7 x 10(5) liter/mol). Binding studies indicate that both the 2-methylnaphthoquinone rings and the phytyl tail of the vitamin K(1) hapten contribute to the total binding energy. The binding of these ligands in the crystalline state has been investigated by difference Fourier maps of Fab' New-ligand complexes at 6-A resolution. A 3.5-A resolution difference Fourier map obtained for the gamma-hydroxy derivative of the vitamin K(1)-Fab' complex shows that this hapten is bound in a shallow groove or crevice between the light and the heavy chains, in close proximity to the polypeptide segments containing the hypervariable regions. At least 12 amino-acid residues from both the light and the heavy chains appear to be in close contact with the ligand. No major conformational changes were detected in the Fab' fragment after ligand binding.
IgG New以低亲和力（K(0)约为1×10³升/摩尔）结合诸如orceine、甲萘醌和尿苷等配体，并以较高亲和力（K(0)=1.7×10⁵升/摩尔）结合维生素K(1)的γ-羟基衍生物。结合研究表明，维生素K(1)半抗原的2-甲基萘醌环和植醇尾均对总结合能有贡献。通过6埃分辨率的Fab' New-配体复合物的差分傅里叶图研究了这些配体在晶体状态下的结合情况。维生素K(1)-Fab'复合物的γ-羟基衍生物的3.5埃分辨率差分傅里叶图表明，该半抗原结合在轻链和重链之间的浅沟或缝隙中，紧邻包含高变区的多肽片段。轻链和重链中至少12个氨基酸残基似乎与配体紧密接触。配体结合后，在Fab'片段中未检测到主要的构象变化。
